1. Field of the Invention
The present invention relates to a filter apparatus, and in particular, to a liquid filter apparatus having fluted filter media.
2. Description of the Prior Art
Filters which are used for filtering gases or liquids are well known and are commonly utilized for many types of filtering applications. Although prior filter devices are able to satisfactorily filter a substantial portion of the particulate and other materials from the fluids, still further improvements are possible. Filter density has become more critical as greater performance is required, while minimizing weight, volume and cost. A longer filter service interval without loss of efficiency has also gained importance.
A common problem with filter designs is inadequate filter surface area. For liquid filters, such as fuel filters, water, oil or coolant filters, the effective filtering surface area for a given volume of filter has not been entirely satisfactory. Pleated filters are commonly used which utilize a pleated filter media. A common liquid filter design which utilizes pleated filter media with radially inward flow is shown in FIGS. 1 and 2. Such filters utilize a pleated filter cartridge which typically mounts in a metal spin-on canister. Although this type of filter does remove a substantial amount of particulate and other matter, it has several disadvantages. A large portion of the internal volume of the filter is wasted space which is not utilized for filtration. The wasted space is due to the manner in which the filter media is pleated and positioned around a perforated central core. The hollow central core is needed to support the filter media and to allow an area for filtered fluid to collect and be directed out of the filter element after passing through the filter media.
Another problem with the pleated filter design is that the nature of pleated filters provides an upper limit as to the amount of filter media which may be positioned around the central core. The smaller the inner diameter of the filter and the center core, the more difficult it becomes to package the media in this manner. The number of pleats becomes too great and the pleats touch at an inner portion. This configuration limits the amount of filter media that can be put in a given volume, thereby causing uneven loading of contaminants on only some portions of the filter media and increasing the pressure drop across the filter. As today's automobiles require longer service intervals, pleated filters are often unable to operate over the extended interval without sacrificing efficiency. In addition, even though the pleats are spaced very tightly at their inner diameter, the pleats are very widely spaced at their outer diameter, as shown in FIG. 2. The gaps are required with the nature of the prior art design and require large space which cannot be used for filter media.
Another drawback to the pleated filter design is that with wide gaps between pleats, it is difficult for the pleats to maintain their positions so that as the filter loads with contaminants, the pleats may shift or bunch. This may cause pressure drop across the filter to increase and may result in failure of the filter. To overcome this problem, filters of this type often have to utilize hot melt beads, wraps of string, or other materials to help maintain the widely spaced pleats in position. However, these measures increase the complexity, weight and costs of such filters.
In addition to the drawbacks of the filtering efficiencies and volume required, conventional fluid filters are relatively complex and require a high number of parts, adding to the component and manufacturing costs. Problems associated with manufacturing include the steps of pleating the filter media prior to positioning around the center core, packing into a cylindrical shape, and forming a seal where the pleats connect. In addition, the center core must provide substantial support to the pleated filter media to withstand the pressure differential which tends to collapse the filters when loading with contaminant. To add additional support, the ends of the filter media generally must be potted with a plastisol material and inserted into metal end caps. Other supports may be placed around the outer diameter of the pleats such as hot-melt beads, wrapping strings or outer liners. A spring is typically utilized in the bottom of a spin-on canister to hold the filter cartridge tightly against an upper seal at the opening to prevent contaminated fluids from bypassing the filter.
It can be seen then that a new and improved liquid filtering apparatus is needed. In particular, the filtering apparatus should be structurally self-supporting to reduce support required for the filter media. In addition, such an apparatus should provide increased filter media for a given volume, thereby decreasing the pressure drop across the filter and the total volume required for the filter. Such a filter should also provide for flexibility in the flow path through the filter element within a canister and decrease the central area within the filter media. Such a device should also reduce the total number of parts and manufacturing complexity of a filter. The present invention addresses these as well as other problems associated with liquid filters.